This invention concerns the manufacture of trim pieces such as instrument panels and steering wheel covers which overlie air bag installations, and more particularly processes for manufacturing trim pieces which have air bag canisters installed behind the trim pieces which are preweakened to allow an inflating air bag to form a deployment opening by forcing a concealed door section of the trim piece to separate and swing out from the adjacent portion of the trim piece structure.
One or more hinged deployment door panels overlying the air bag have long been incorporated in such auto trim pieces, which are held closed by tabs or other elements and are then forced open by the inflating air bag when the air bag is deployed.
In recent years, so called xe2x80x9cinvisible seamxe2x80x9d installations have been developed, in which the separate visibly delineated doors initially used have been eliminated, and a smooth overlying covering extends over the trim piece location whereat the air bag is mounted.
An opening is formed in the trim piece when the air bag is activated by the inflating air bag forcing itself through a section of the trim piece. This is accomplished by a preweakening of the trim piece at the air bag location to allow the pressure of the inflating air bag to cause a xe2x80x9cdoorxe2x80x9d tear in the trim piece to break free and hinge open along one side.
Trim pieces are often constructed in layers including a stiff substrate panel, and overlying skin and foam covering layers, or with a skin bonded to a substrate panel.
The substrate may be molded first, and the skin and foam added subsequently.
The preweakening has involved the formation of preweakening grooves in the trim piece and/or covering layers molded into the piece, or the formation of the grooves as by laser scoring of the trim piece or components thereof.
A separate door panel is often fit into an opening molded into the substrate panel, but this requires additional processing steps.
Cutting through a substrate panel to form the door has also been practiced, but this requires a powerful cutting apparatus to sever the relatively thick substrate, increases cycle time, and in the case of laser cutting, requires handling of the by-products generated by vaporizing of the substrate material.
It is the object of the present invention to provide a simplified method of manufacturing an automotive trim piece which is preweakened to form an invisible seam deployment door opening for air bags.
The above object and other which will be understood upon a reading of the following specification and claims is achieved by a process in which a substrate panel is preformed with one or more deployment door panels, each integrally connected along one side to adjacent portions of the substrate panel, and with a gap spacing the unconnected door sides from the adjacent substrate sections. The connected side of the door panel functions as a hinge when the panel is contacted by the inflating air bag.
Bridging tabs may optionally be formed extending across the gap at one or more locations to stabilize the panel with respect to the rest of the substrate panel.
The one or more covering layers are later added or formed at the same time to overlie the substrate panel. The covering layers may also be cut or scored as by directing a laser beam or other scoring or cutting agent through and along the gap, and tracing along the path of the gap in a door pattern, to preweaken the covering layer in a pattern corresponding to the free, unhinged sides of the door sections.